Surgical clips (also referred to as tissue clip) are medical implants that are used in most cases temporarily for closing tissue perforations, for example, or for the treatment of aneurysms as vessel clips. For this purpose a plurality of clip shapes are suited starting with jaw-like clips in which the clamping or clip branches are in the form of two opposed longitudinally curved rows of teeth similarly to the upper and lower jaws, which are coupled to each other via hinges at their respective two longitudinal ends, up to row-shaped (straight) clips that include two opposed substantially straight clamping rails comparable to conventional forceps, the clamping attachments being provided with teeth or a corrugation, where appropriate, and being coupled to each other hinge-like at one respective longitudinal end only.
All known clip shapes have in common, however, at least one spring arrangement applying a clamping force to the clip branches. This at least one spring arrangement can be a separate component inserted in the clip so as to pre-stress the clip branches against each other or it is integrated (in one piece) in the clip. In the latter case the spring arrangement substantially forms the hinge or hinges to which the two clip branches are pivoted.
From the state of the art a surgical clip of the species having straight clip branches and a one-sided spring arrangement is known, as it is published in DE 20 2010 008 512 U1, for example.
The clamping or closing force is generated in this case by a leg spring in the form of either a round or a rectangular spring. Concretely speaking, such clip consists of two clip branches that are loosely intersecting (i.e. without any mechanical connection such as a hinge pin) in their respective central portions so as to form two clamping portions adjacent in parallel in the closing position and two actuating legs or actuating portions spaced apart from each other in this position. The free ends of the actuating portions are interconnected by the afore-mentioned leg spring which is formed either integrally (of one single part) with the clip branches or as separate component and then is connected (soldered, welded, put together etc.) to the clip branches so as to form one member. The leg spring may have either half a winding, a 1.5 fold or even 2.5 fold winding.
For operation the surgical clip is compressed at its actuating portions, thereby the clamping portions being spaced apart from each other due to the intersecting orientation of the clip branches. At the same time the leg spring is biased more strongly. When the actuating portions are released, the leg spring causes the actuating portions to be urged apart until the clamping portions are pressed against each other.
Although the afore-mentioned design ensures sufficiently high pressing force between the two clamping portions and the leg spring is little loaded due to an only small elastic degree of deformation and therefore is very long-living, there are still resulting several drawbacks.
The use of the leg spring requires a comparatively expensive and difficult manufacturing process for winding the spring which has to be carried out without the spring material forming cracks. In this case, too, there is the possibility of rewinding the leg spring, thereby the pressing force between the clamping portions being reduced. In total, the manufacture of the leg spring therefore requires a high degree of precision so as to manufacture instruments the characteristics of which (pressing force, lifetime, reliability etc.) are within a narrow tolerance range. Therefore the scrap rate is correspondingly high. All afore-mentioned and further drawbacks of the known surgical clip finally result in a comparatively high price for the surgical clip.
Further surgical clips of this species are also known from U.S. Pat. No. 6,179,850 B1 or EP 0 122 046 A1, for example.
From a further state of the art document according to DE 20 2010 008 714 U1 a surgical clip is known comprising two clip branches extending in parallel to each other without intersecting and being interconnected in their respective central areas via a land-like flexural spring. Accordingly, the clip branches are extended beyond the flexural spring in the longitudinal direction thereof and thus form two clamping portions on the one side of the flexural spring and two actuating legs/portions on the other side of the flexural spring, for example according to the principle of a generally known peg. When the two actuating portions are thus pressed against each other on the one side of the land-like flexural spring, the two clamping portions are moving apart on the other side of the flexural spring and vice versa.
This surgical clip is manufactured of one single part according to an injection molding process and is thus relatively inexpensive as regards its manufacture. In contrast to the afore-described clip, the fabrication can be carried out substantially automatically and thus inexpensively by the injection molding process. The biasing of the flexural spring in the closed position of the clip is obtained by a locally differing material shrinkage upon hardening of the injection molded material in accordance with this disclosure. In this way, a comparatively high quality standard can be reached in a simple manner. However, this solution has drawbacks as well.
Although the flexural spring has an open annular shape bulging in the direction of the actuating portions, the deformation path/degree of the flexural spring in normal use is comparatively large so that the spring can rapidly fatigue. Moreover, the flexural stress is by far higher vis-à-vis the leg spring, which also results in more frequent spring fractures. Finally this is resulting in lower reliability and service life compared to the leg spring. In particular, it has also turned out to be difficult to attain sufficient reproducible clamping forces by the afore-described non-symmetric material shrinkage.
Furthermore, in the state of the art efforts have been made to arrange the annular or U-shaped flexural spring at the respective outer ends of the clip branches so that clamping and actuating portions of each clip branch are located on the same side of the spring and thus have the same direction of movement when the clip is actuated (and not opposed directions as in the aforementioned state of the art). In this case the clip is spread by pulling the actuating portions apart and not by compressing them as in the state of the art cited in the beginning. This entails the fact that the clip becomes unhandy and non-ergonomic, thereby its field of use being definitely reduced. Alternatively there is basically the option to cross the branches so that compressing the actuating portions causes the clamping portions to open. However, also in this case at least the biasing force of the spring has turned out to be comparatively small so that the material strength of the spring had to be increased. Therefore the clip is in total dimensioned so large that it is suited for specific purposes only.
Another surgical clip is known from DE 198 58 580 C1. The clip described there is U-shaped and includes two clip branches extending in parallel without intersecting and being interconnected in their respective central areas via a land-shaped flexural spring. A detent means of the clip fixes the land upon compression of the clip branches so as to bring about comparatively high retaining forces. However, in this case too, it has turned out to be difficult to generate sufficiently reproducible clamping forces.